Reliability of the Lateral Step-Up Test and Its Correlation with Motor Function and Activity in Chronic Stroke Survivors

Background. The Lateral Step-Up Test (LSUT) has been used to evaluate the closed kinetic chain functional muscle strength in people with orthopaedic or neurological conditions. No study has systematically investigated the intrarater, interrater, and test-retest reliabilities of this measure in stroke survivors. In addition, correlations of the LSUT count with other stroke-specific impairment and function measurements remain unidentified. Objectives. This study was aimed at investigating (1) the interrater, intrarater, and test-retest reliability of the LSUT; (2) minimum detectable change in LSUT counts; and (3) correlation between LSUT counts and stroke-specific impairment and function measurements. Methods. Thirty-three stroke survivors were assessed with LSUT and a battery of stroke-specific impairment and function measurements, including Fugl-Meyer assessment of lower extremity (FMA-LE), lower limb muscle strength, Five Times Sit-to-Stand Test (FTSTS), Berg Balance Scale (BBS), Timed Up and Go Test (TUG), and Activities-specific Balance Confidence (ABC) scale, by two assessors. Their performance on LSUT was reassessed 1 week later to establish the test-retest reliability. The intraclass correlation coefficient (ICC) was used to assess the reliability of LSUT, and Spearman's rho was used to quantify the strength of correlations between LSUT counts and secondary outcomes. Results. The LSUT counts exhibited good to excellent intrarater, interrater, and test-retest reliability (ICC: 0.869-0.991). The minimum detectable change in the average LSUT count was 1 step. LSUT counts correlated significantly with the FMA-LE score, lower limb muscle strength (except for the hip abductors), FTSTS time, BBS score, TUG time, and ABC score. Conclusions. The LSUT is a reliable, valid, and easily administered measure of the closed kinetic chain functional muscle strength of stroke survivors.